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23 Cards in this Set
- Front
- Back
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what are the stages in tooth development? (6)
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formation of dental lamina
bud stage cap stage bell stage crown formation root formation |
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odontogenesis of the primary teeth begins when?
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week 6
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what happens at the stage of the formation of dental lamina?
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Ectoderm lining the stomodeum gives rise to the oral epithelium= this arch of epithelium (corresponding dental arch) thickens giving rise to Dental Lamina
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when does the bud stage start?
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approx. week 8
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what happens at the bud stage?
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extensive proliferation of the dental lamina to form oval shaped masses (buds) which penetrate into underlying mesenchyme
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how many places in the mouth do the buds form?
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10 places for upper and lower (= dental arch of deciduous)
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at what stage does the cap start?
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weeks 9 + 10
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what happens at the cap stage?
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continued proliferation becomes uneven resulting in the formation of cap shape still attached to dental lamina
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when does the bell stage happen?
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11 + 12 weeks
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what happens at the bell stage?
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mass of epithelial cells transform into morphologically and functionally distinct components.
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what are the components involved in the bell stage? (4)
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outer enamel epithelium (OEE)
inner enamel epithelium (IEE) stellate reticulum stratum intermedium |
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what is the outer enamel epithelium (OEE)?
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Their primary function is to serve as a protective barrier for the enamel organ
epithelial cells on the outer surface of the enamel organ become cuboidal in shape |
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what is the Inner enamel epithelium (IEE)?
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these cells go on to further differentiate into ameloblasts that form the enamel metrix
epithelial cells on the inner surface of the enamel organ become elongated or tall and columnar shaped |
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what is the stratum intermedium?
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primary role is a supportive one in the production of enamel matrix
cells adjacent to the IEE form a compressed layer of flat to cuboidal cell |
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what is the stellate reticulum?
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remainder of cells between the IEE and OEE form the stellate reticulum- secrete hydrophilic ground substance with pulls water INTO the dental organ
this water forces cells apart giving "star" appearance cells also support formation of the enamel matrix. |
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what happens in crown formation stage?
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final stages of odontogenesis are apposition (lay down of materials for enamel) and maturation (mineral content increases, water content decreases) where we have production of enamel and dentine
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what happens in root formation stage?
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the cervical loop= IEE and OEE grow further apically
Stratum intermedium and stellate reticulum are not involved in this stage due to the root having NO ENAMEL |
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what is the hertwig's root sheath?
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formed from cervical loop
extends apically to map out the anatomy of the root and results in apical development of the root dentine |
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what happens as each stage of dentine is complete?
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the underlying basement membrane and the root sheath disintegrates
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what does the root sheath remnants remain as?
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islands of cells known as epithelial rests of Malassez
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what happens at tooth eruption?
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throughout the process of apposition of enamel, the SI and SR decrease and when apposition is complete the ameloblasts (originally IEE) and OEE fuse together to form reduced enamel epithelium (REE)
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explain REE?
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enzymes are produced from the REE which break down the central portion of the fused cellular tissue creating a canal that communicates with oral cavity which the tooth will erupt
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what happens as tooth erupts?
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cellular layer on the crown of the tooth peels back and integrates with the oral mucosa
only a few cells remain attaches to enamel which is immediately coronal to CEJ- also known as JE (junctional epithelium) |
